This diagram presents a simplified view of the four primary DNA bases: adenine (A), guanine (G), cytosine (C), and thymine (T), highlighting their chemical structures and classifications as purines or pyrimidines. A central illustration depicts the DNA double helix, showing complementary base pairing of A with T and C with G. Insets detail the molecular structures of each base, labeled with their chemical elements and grouping them into purines (large double-ring structures) and pyrimidines (single-ring structures). The color-coded boxes and arrows clarify how base pairs align within the DNA helix, enhancing understanding of DNA’s molecular composition and pairing rules.